This invention is directed generally to a trailer for storing or transporting elongated cylindrical fluid containers and specifically to a trailer for tubes for containing compressed gas. Such trailers are intended to be attached to and drawn by a tractor. Trailers have a flat horizontal frame on which, pursuant to prior art, a bottom layer of tubes is supported. Succeeding layers are stacked up with lower tubes supporting those above to form a compact bundle. Often, supports are provided at spaced intervals along the tube length and retainers are used to secure the bundle to the frame. Sometimes the tubes are retained at least in part at their ends between a front bulkhead and a rear bulkhead which are attached to the frame. The tubes have a reduced diameter at each end which protrude through openings in the bulkheads and are mechanically attached to the bulkheads. Usually the tube ends bear an external thread on which nuts are threaded to clamp the tubes to the bulkheads. At one end of the trailer, the tube ends are manifolded and piping is provided for supplying gas to, and withdrawing compressed gas from, the tubes.
A problem encountered in bundles where tubes contact or are contacted by intermediate supports is that rusting occurs at the contact points. This problem is obviated by supporting the tubes solely at their ends and providing a clearance space between the tubes, an arrangement shown in U.S. Pat. No. 2,761,397 issued to Holst.
Periodically, the tubes must be tested for structural integrity. A bundle where tubes support each other must be disassembled to allow hydrostatic testing of each tube, which is an expensive, lengthy procedure. The development of acoustic emission techniques offers an alternative to hydrostatic testing, providing the tube surface is accessible for the placement of sensors and no supports exist along the tube length to interfere with the transmission and analysis of the acoustic emission signals. Thus, spacing the tubes and supporting them solely at their ends as shown by Holst allows acoustic testing. However if a tube needs to be replaced, the Holst arrangement still requires disassembly of the tube bundle.
The above disadvantage is partially overcome by the modular arrangement shown in U.S. Pat. No. 4,784,399 issued to Finn. Finn stacks horizontally extending modules of tubes to build up a tube bundle. This arrangement creates joints between modules which are subject to high shear loads imposed by the inertial forces developed by the tubes during starting, stopping and changing direction of the trailer. To take up some of this loading, Finn relies on vertical rods which help stabilize and unify the tube modules. Also, in Finn's arrangement, when a tube in a lower position needs to be removed for maintenance or replacement, all of the tube modules above the module containing the defective tube must be removed. These and other disadvantages experienced with prior art tube trailers are obviated by the present invention.
A principal object of the present invention is to provide a tube trailer wherein the tubes are supported in modules which can be individually removed from the trailer and which will facilitate removal of any tube.
Another object of the invention is to provide tube modules which can be readily affixed to the trailer frame and are inherently accommodative of inertial loads imposed by the tubes.
Another object of the invention is to provide a tube trailer wherein the tubes are spaced to allow some types of testing and maintenance without module removal and disassembly.
Still another object is to provide a tube trailer in which valves mounted in the ends of the tubes are shielded by the tube support structure from physical damage by outside agencies approaching from the side of a tube module.
With these and other objects in view, as will be apparent to those skilled in the art, the present invention resides in the combination of parts as set forth in the specification and particularly pointed out in the claims.